The Battle of Towton was fought during the English Wars of the Roses on 29 March 1461, near the village of the same name in Yorkshire. It was the "largest and bloodiest battle ever fought on English soil". According to chroniclers, more than 50,000 soldiers from the Houses of York and Lancaster fought for hours amidst a snowstorm on that day, which was a Palm Sunday. A newsletter circulated a week after the battle reported that 28,000 died on the battlefield. The engagement brought about a monarchical change in England — Edward IV displaced Henry VI as King of England, driving the head of the Lancastrians and his key supporters out of the country.
More information on the Wikipedia page [1]. Historic UK page here, British Battles here and ?UK Battlefields Resources Centre here.